【摘要】 草地退化是内蒙古主要生态问题之一。为此，内蒙古自2000年起实施了一系列以放牧管理为核心的草地保护政策，然而在干旱加剧背景下，这些政策如何通过调控放牧活动影响草地总初级生产力(GPP)对干旱的响应过程及其时空特征仍不明确。系统评估了1992—2018年放牧政策转型与干旱胁迫对内蒙古草甸草原、典型草原和荒漠草原GPP的协同作用及影响路径。结果表明：(1)1992—2018年内蒙古草地GPP整体呈不显著下降趋势(56.54%),其中荒漠草原GPP呈上升趋势(53.56%)。SPEI指数整体下降(95.54%),在放牧政策实施第一阶段(2000—2010)干旱情况最严重，SPEI值多低于-0.5。放牧强度总体下降(95.88%),但在自由放牧时期(1992—1999),放牧强度呈上升趋势(54.97%)。(2)从自由放牧时期(1992—1999)到放牧政策实施第二阶段(2011—2018),SPEI的重要性呈先升后降趋势，而放牧强度的重要性则先降后升。GPP和SPEI整体呈正相关关系(89.01%),但其相关性随草地类型和时期不同而有所差异。(3)放牧强度和SPEI对草地GPP变化均有显著直接影响。随着政策实施，SPEI的直接影响逐渐减弱，而放牧强度的影响则由负转正。研究结果在一定程度上证实了放牧政策转型对草地生态系统恢复的积极作用。更多还原

【Abstract】 Grassland degradation is one of the main ecological issues in Inner Mongolia. To combat this issue, Inner Mongolia has launched a series of grassland protection policies centered around grazing management since the early 2000s. However, how these policies regulate grazing activities to influence the response of grassland gross primary productivity(GPP) to drought and its spatiotemporal characteristics remains unclear. This study systematically evaluated the synergistic effects and impact pathways of grazing policy transformation and drought stress on the GPP of meadow steppe, typical steppe, and desert steppe in Inner Mongolia from 1992 to 2018. The results showed that:(1) From 1992 to 2018, the GPP of grassland in Inner Mongolia exhibited an overall insignificant declining trend(56.54%), while the GPP of desert steppe showed an increasing trend(53.56%). The Standardized Precipitation Evapotranspiration Index(SPEI) exhibited an overall declining trend(95.54%), with the most severe drought conditions occurring during the first phase of grazing policy implementation(2000—2010), where most SPEI values were lower than-0.5. Grazing intensity generally declined(95.88%), but during the free grazing period(1992—1999), it showed an increasing trend(54.97%).(2) From the free grazing period(1992—1999) to the second phase of grazing policy implementation(2011—2018), the importance of SPEI first increased and then decreased, while the importance of grazing intensity first decreased and then increased. GPP and SPEI were generally positively correlated(89.01%), but their correlation varied across different grassland types and periods.(3) Both grazing intensity and SPEI had significant direct impacts on grassland GPP. As policy implementation progressed, the direct impact of SPEI gradually weakened, while the influence of grazing intensity shifted from negative to positive. The study results confirm, to some extent, the positive role of grazing policy transformation in restoring grassland ecosystems.更多还原